Just started noticing this — when two players play their instruments in sync, notes (especially in chords) are being cancelled out (not from skill recharge). This is a little saddening for those playing duets. I have recorded lots of duets in the past without running into this problem. Other players I know have been running into this as well.
The following link is a video taken featuring Harp and Lute playing the same chord (Middle Octave: 1358) together. Enough chords make it together (lol) to hear the cancellation. Easier to hear it near the end: